I note this on the CAA website (
http://www.caa.co.uk/default.aspx?ca...08&faqid=359):
Summary
If you need medication the underlying medical condition will often make you unfit to fly
If you need medication to ‘make you feel better’ you should not be flying unless your authorised medical examiner or medical adviser (who knows you are a pilot) has approved its use. Professional pilots should take advice from a doctor experienced in aviation medicine.
If you have been taking a medication that can affect judgement, especially those with drowsiness or dizziness listed as potential side effects, a suitable period should elapse after the last dose to enable any effects to dissipate. If the dosage regime is ‘every 4-6 hours’ do not fly until 12 hours has elapsed after the last dose. If dosage is ‘every 10-12 hours’ do not fly for 24 hours
You might argue - I would - that in declaring to my AME that I was using cetirizine at the medical, I was asking my 'authorised medical examiner' to 'approve its use.' Indeed, we discussed it - briefly - and he didn't raise any concerns. I could ring him up to discuss it, but that letter from the CAA effectively closes that door.
On the other hand, the last paragraph basically rules out any drugs on a once-per-24-hours basis, such as the one I was taking (Boots own brand).
Off to find Telfast, anyway.
Tim
(PS edited to add: I talked about side-effects to a medical researcher once who said that basically, anything that happens to any of the test subjects during the drug trial becomes listed as a side-effect. So every drug causes headaches, because at some point during the trial, someone's bound to have one..!)